Precoding for segment sensitive scheduling in wireless communication systems

ABSTRACT

Techniques to enhance the performance in a wireless communication system using segments called subbands and using precoding are shown. According to one aspect, the bandwidth for transmission to an access terminal is constrained to a preferred bandwidth which is less than the bandwidth available for transmission to an access terminal and precoding information related to the subcarriers within the constrained bandwidth is provided to a transmitter. The precoding information related to the subcarriers within a constrained bandwidth provides feedback about the forward link channel properties relative to different subbands and may be fed back on a channel associated with the bandwidth.

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

The present Application for Patent is a continuation of patentapplication Ser. No. 11/553,870, entitled “PRECODING FOR SEGMENTSENSITIVE SCHEDULING IN WIRELESS COMMUNICATION SYSTEMS”, filed Oct. 27,2006, now allowed, which claims priority to Provisional Application No.60/731,558 entitled “SEGMENT SENSITIVE SCHEDULING FOR PRECODING INWIRELESS COMMUNICATION SYSTEM” filed Oct. 27, 2005, and assigned to theassignee hereof and hereby expressly incorporated by reference herein.

BACKGROUND

1. Field

The present description relates generally to wireless communication andmore specifically to precoding in a wireless communication system.

2. Background

Wireless communication systems are widely deployed to provide varioustypes of communication such as voice, data, and so on. These systems maybe multiple-access systems capable of supporting communication withmultiple access terminals by sharing the available system resources(e.g., bandwidth and transmit power). Examples of such multiple-accesssystems include code division multiple access (CDMA) systems, timedivision multiple access (TDMA) systems, frequency division multipleaccess (FDMA) systems, and orthogonal frequency division multiple access(OFDMA) systems. Typically, a wireless communication system comprisesseveral base stations, wherein each base station communicates with themobile station using a forward link and each mobile station (or accessterminal) communicates with base station using a reverse link.

A problem in many communication systems is the receiver is located in aspecific portion of an area served by the access point. In such cases,where a transmitter has multiple transmit antennas, the signals providedfrom each antenna need not be combined to provide maximum power at thereceiver. In these cases, there may be problems with decoding of thesignals received at the receiver. One way to deal with these problems isby utilizing precoding.

Precoding is a spatial processing technique that improves thesignal-to-noise ratio (SNR) of a wireless link with multiple antennas.Typically, precoding may be used at the transmitter in a multipleantenna system. Precoding provides many advantages in improvingsignal-to-noise ratios which improves the decoding of the signals by thereceiver.

Certain types of OFDMA systems are frequency division duplexed (FDD)OFDMA systems. In these FDD OFDMA systems, the transmission from theaccess point to the access terminal and from the access terminal to theaccess point occupy different distinct frequency bands. In FDD OFDMAsystems feedback to perform precoding generally requires knowledge ofthe channel at the transmitter, e.g. access point, which is notavailable without substantial feedback. This feedback, generally in theform of the actual weights or vectors, requires a large amount ofresources on control or signaling channels. This reduces data rates andincreases the overhead required.

Thus, there exists a need in the art for a system and/or a methodologyto enhance the performance of precoding.

SUMMARY

The following presents a simplified overview or summary of one or moreaspects in order to provide a basic understanding of such aspects. Thissummary is not intended to be an extensive overview of all contemplatedaspects, and it is not intended to identify key or critical elements ofall aspects nor is it intended to delineate the scope of any or allaspects. Its sole purpose is to present some concepts of one or moreaspects in a simplified form as a prelude to the more detaileddescription that is presented later.

In an aspect, a wireless communication apparatus comprises a processorconfigured to decode signals that are received over two or moresubcarriers of a segment of subcarriers, which is one of a plurality ofsegments of subcarriers available for communication, and to provideprecoding information for at least one segment. In addition theapparatus comprises a transmitter configured to transmit the precodinginformation.

In another aspect, a method comprises receiving signals over two or moresubcarriers of a segment of subcarriers, which is one of one or moresegments of subcarriers. The method further comprises generatingprecoding information for at least one segment and transmitting theprecoding information.

In a further aspect, an apparatus comprises means for receiving signalsover two or more subcarriers of a segment of subcarriers, which is oneof one or more segments of subcarriers. The apparatus further comprisesmeans for generating precoding information for at least one segment andmeans for transmitting the precoding information.

In an aspect, a computer program product comprises a computer readablemedium including instructions for receiving signals over two or moresubcarriers of a segment of subcarriers, which is one of one or moresegments of subcarriers. The medium further comprises instructions forgenerating precoding information for at least one segment andinstructions for transmitting the precoding information.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, nature, and advantages of the present aspects may becomemore apparent from the detailed description set forth below when takenin conjunction with the drawings in which like reference charactersidentify correspondingly throughout and wherein:

FIG. 1 illustrates aspects of a multiple access wireless communicationsystem according to an aspect;

FIG. 2 illustrates aspects of a spectrum allocation;

FIG. 3 illustrates aspects of another spectrum allocation.

FIG. 4 illustrates a methodology for performing feedback of precodinginformation for subcarrier segments.

FIG. 5 illustrates an apparatus for reporting precoding information forsubcarrier segments.

FIG. 6 illustrates aspects of a transmitter and receiver in a multipleaccess wireless communication system.

DETAILED DESCRIPTION

Various aspects are now described with reference to the drawings,wherein like reference numerals are used to refer to like elementsthroughout. In the following description, for purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of one or more aspects. It may be evident; however, thatsuch aspect(s) may be practiced without these specific details. In otherinstances, well-known structures and devices are shown in block diagramform in order to facilitate describing one or more aspects.

As used in this application, the terms “component,” “system,” and thelike are intended to refer to a computer-related entity, eitherhardware, a combination of hardware and software, software, or softwarein execution. For example, a component may be, but is not limited to, aprocessor, a process running on a processor, an object, an executable, athread of execution, a program, and/or a computer. One or morecomponents may reside within a process and/or thread of execution and acomponent may be localized on one computer and/or distributed betweentwo or more computers. Also, these components can execute from variouscomputer readable media having various data structures stored thereon.The components may communicate by way of local and/or remote processessuch as in accordance with a signal having one or more data packets(e.g., data from one component interacting with another component in alocal system, distributed system, and/or across a network such as theInternet with other systems by way of the signal).

Furthermore, various aspects are described herein in connection with auser device. A user device can also be called a system, a subscriberunit, subscriber station, mobile station, mobile device, remote station,access point, base station, terminal, remote terminal, access terminal,user terminal, user agent, or user equipment. A user device can be acellular telephone, a cordless telephone, a Session Initiation Protocol(SIP) phone, a wireless local loop (WLL) station, a PDA, a handhelddevice having wireless connection capability, or other processing deviceconnected to a wireless modem.

Moreover, various aspects or features described herein may beimplemented as a method, apparatus, or article of manufacture usingstandard programming and/or engineering techniques. The term “article ofmanufacture” as used herein is intended to encompass a computer programaccessible from any computer-readable device, carrier, or media. Forexample, computer readable media can include but are not limited tomagnetic storage devices (e.g., hard disk, floppy disk, magnetic strips. . . ), optical disks (e.g., compact disk (CD), digital versatile disk(DVD) . . . ), smart cards, and flash memory devices (e.g., card, stick,key drive . . . ).

Referring to FIG. 1, a multiple access wireless communication systemaccording to one aspect is illustrated. A multiple access wirelesscommunication system 100 includes multiple cells, e.g. cells 102, 104,and 106. In the aspect of FIG. 1, each cell 102, 104, and 106 mayinclude an access point 150 that includes multiple sectors. The multiplesectors may be formed by groups of antennas each responsible forcommunication with access terminals in a portion of the cell. In cell102, antenna groups 112, 114, and 116 each correspond to a differentsector. In cell 104, antenna groups 118, 120, and 122 each correspond toa different sector. In cell 106, antenna groups 124, 126, and 128 eachcorrespond to a different sector.

Each cell includes several access terminals which may be incommunication with one or more sectors of each access point. Forexample, access terminals 130 and 132 are in communication base station142, access terminals 134 and 136 are in communication with access point144, and access terminals 138 and 140 are in communication with accesspoint 146.

It can be seen from FIG. 1 that each access terminal 130, 132, 134, 136,138, and 140 is located in a different portion of it respective cellrelative to other access terminal in the same cell. Further, each accessterminal may be a different distance from the corresponding antennagroups with which it is communicating. Both of these factors providesituations, due to environmental and other conditions in the cell, whichcause different channel conditions to be present between each accessterminal and the corresponding antenna group with which it iscommunicating.

Spatial multiplexing with linear precoding is a technique used to takeadvantage of the high spectral efficiency provided by multiple-inputmultiple-output (MIMO) systems or other multiple transmission antennatechniques. This can be implemented over frequency selective channels byusing OFDM. In frequency division duplexing (FDD) systems the forwardand reverse links are not reciprocal. Therefore, feedback of channelstate information (CSI) at the transmitter in the form of precodingmatrices is required. In MIMO-OFDM with precoding, a broadband channelis converted into multiple narrowband channels corresponding to OFDMsubcarriers. The MIMO-OFDM transmitter requires feedback in the form ofprecoding matrices for the subcarriers. A general technique of precodingwhere the selection of an index that identifies the matrix(ces) orvector(s) comes from a defined codebook known to both the transmitterand receiver may be used. In some aspects the selection of the codebookentries may determined by selecting a matrix(ces) or vector(s), whichprovides a gain, signal-to-noise ratio (SNR), channel conditions, or thelike that fulfills some criteria. In some cases, the criteria may be abest value, as determined by a device or system design. In anotheraspect, a threshold may be used to determine what matrix(ces) orvector(s) to select. In another aspect, an average of the channelcriteria, e.g. SNR, for a subcarrier segment, e.g. a subband, isdetermined in order select a matrix(ces) or vector(s). In addition otherchannel criteria or combinations of multiple channel criteria may beutilized to select a matrix(ces) or vector(s).

As used herein, an access point may be a fixed station used forcommunicating with the terminals and may also be referred to as, andinclude some or all the functionality of, a base station, a Node, orsome other terminology. An access terminal may also be referred to as,and include some or all the functionality of, a user equipment (UE), awireless communication device, a terminal, a mobile station or someother terminology.

A MIMO design may have two modes of operation, single code word (SCW)and multiple-code word (MCW). In MCW mode, the transmitter can encodethe data transmitted on each spatial layers, i.e. streams,independently, possibly with different rates. In a SCW mode design, thetransmitter encodes the data transmitted on each spatial layer with“identical data rates.”

Referring to FIG. 2, in an OFDM system, for a given bandwidth, forexample a 5 MHz bandwidth, an access terminal will decode a signal orsignals which may be transmitted on two or more subcarriers 306 of asubcarrier segment 302 ₁. The group of subcarriers used for a giventransmission to an access terminal, is generally less than all of thesubcarriers 308 of segment 302 ₁. Thus, a subcarrier set 308 of a givensegment 302 _(N) allows users to be scheduled on a portion of the entire5 MHz bandwidth that has better channel quality for the terminal, lesstraffic, a combination of these, or some other criteria.

In frequency hopping communication, a terminal may be scheduled to hop,in order to provide frequency diversity, over the subcarriers 308 of asegment 302 _(N). The frequency hopping may vary on a frame by frame,superframe by superframe, or some other basis. The frequency hopping mayinclude assignment of blocks of contiguous subcarriers, block hopping,or distributed subcarriers, symbol hopping.

Performing frequency hopping within a segment allows the access terminalto calculate its preferred precoding matrix(ces) or vector(s) for arange less than the available bandwidth. This can improve the SNR orother characteristic that is used to calculate the precoding gain.

In an aspect, the segment may be a subband which may comprise apredetermined bandwidth. In an aspect, the subbands may have a bandwidthof 1.25 MHz. Thus, with a usable bandwidth of 5 MHz, there could be upto 4 subbands, per carrier. Although other sizes of usable bandwidth andsegments, e.g. subbands, may be utilized. An access terminal operatingprovides feedback information for a segment may calculate a qualitymetric, e.g. SNR, that would result in a precoding gain, e.g. due tobetter frequency coherence, that provides a better signal andpotentially increased throughput and signal quality.

In FIG. 2, there are 4 subbands 302 ₁-302 ₄, for a 5 MHz deployment.However, the number of subbands may vary, and they need not be the samesize. Further, the subbands need not have the same number ofsubcarriers, and need not comprise adjacent subcarriers.

In further aspects, the segments may be the size of an assignment to theuser, e.g. a block of tones and thus the user may report the precodinginformation for only the subcarriers where it is scheduled. In furtheraspects, the segments may change over time based upon assignments orother instructions generated at the access point and provided to theterminal.

Referring to FIG. 3, a feedback channel sometimes called a channelquality indication (CQI) channel 406 may be used to provide feedback ofprecoding, e.g. an index(ces), vector(s), or matrix(ces) along withother CQI type feedback. An access terminal which could use a widerfrequency bandwidth, for example, a bandwidth 404, may have at least oneCQI transmission channel for each segment. In one aspect, one or moreprecoding index(ces), vector(s), or matrix(ces) may be reported formultiple segments for a single user, even those on which the user is notscheduled, depending on the structure. That is, if each segment, has itsown feedback channel a user may provide feedback, e.g. precodingindex(ces), vector(s), or matrix(ces), for each of the segments on itsor another segments feedback channel.

The CQI, index(ces) vector(s), or matrix(ces) may be transmitted on aCDM channel in order to multiplex multiple users over the sametime-frequency resources and increase bandwidth available for datatransmissions. As a result the number of feedback transmissions, whichcan be sent may be limited by the number of available codes. Thus, whena system is partially loaded, there are codes available to be used as aCQI, and when the system is fully loaded there may be no codes availablethat can be used as a CQI. Thus, by using the codes available on apartially loaded system a precoding gain is achievable by being able toreport feedback in multiple CQI channels for multiple carriers or othersegments into which the reverse link bandwidth may be divided. Inanother aspect, a control channel called reverse subband feedbackchannel (R-SFCH) is introduced. This channel could be used by the accessterminal to indicate the preferred subband.

Referring now to FIG. 4, a methodology for illustrates a methodology forperforming feedback of precoding information for subbands isillustrated. At 502, an access terminal receives a transmission in asegment. This may be provided by scheduling only portions of a channeltree, or a channel tree that solely, correspond to a segment.Alternatively, the segment may be defined by a preferred set ofsubcarriers or some other method. At 504, precoding matrix(ces) orvector(s) are determined or calculated. The determination may be basedupon a selected CQI-precoding matrix calculation from a look-up table orsome other operation. Further, this may be calculated for one or moresegment, or only the segment that the terminal is scheduled. This may bedetermined by the terminal, or part of the assignment or overheadinformation provide by the access point to the terminal.

At 506, the selected precoding matrix(ces) or vector(s) are feedback tothe access point via one or more feedback channels. As discussed above,the feedback channels used may relate to the subband, or subbands, towhich the precoding information relate or some other channels.

Referring now to FIG. 5, an apparatus for reporting precodinginformation for a subband is illustrated. Means 702 for receiving, at anaccess terminal, a transmission in a segment is provided. This may beprovided by scheduling only portions of a channel tree, or a channeltree that solely, correspond to a segment. The means 702 may be incommunication with means 704 for determining, or calculating, precodingmatrix(ces) or vector(s). The determination may be based upon a selectedCQI-precoding matrix calculation from a look-up table or some otheroperation. Further, this may be calculated for one or more segments, oronly the segment that the terminal is scheduled. This may be determinedby the terminal, or part of the assignment or overhead informationprovide by the access point to the terminal.

Means 606, which may be in communication with both means 702 and 704,may transmit the selected precoding matrix(ces) or vector(s) as feedbackto the access point via one or more feedback channels. As discussedabove, the feedback channels used may relate to the segment, orsegments, to which the precoding information relate or some otherchannels.

Referring to FIG. 6, aspects of a transmitter and receiver in a multipleaccess wireless communication system 200 is illustrated. At transmittersystem 210, traffic data for a number of data streams is provided from adata source 212 to a transmit (TX) data processor 214. In an aspect,each data stream is transmitted over a respective transmit antenna. TXdata processor 214 formats, codes, and interleaves the traffic data foreach data stream based on a particular coding scheme selected for thatdata stream to provide coded data. In some aspects, TX data processor214 applies precoding weights to the symbols of the data streams basedupon the user to which the symbols are being transmitted to and theantenna from which the symbols are being transmitted from based on theparticular users channel response information. In some aspects, theprecoding weights may be generated based upon an index to a codebookgenerated at the transceiver 254 and provided as feedback to thetransceiver 222 which has knowledge of the codebook and its indices.Further, in those cases of scheduled transmissions, the TX dataprocessor 214 can select the packet format based upon rank informationthat is transmitted from the user.

The coded data for each data stream may be multiplexed with pilot datausing OFDM techniques. The pilot data is typically a known data patternthat is processed in a known manner and may be used at the receiversystem to estimate the channel response. The multiplexed pilot and codeddata for each data stream is then modulated (i.e., symbol mapped) basedon a particular modulation scheme (e.g., BPSK, QSPK, M-PSK, or M-QAM)selected for that data stream to provide modulation symbols. The datarate, coding, and modulation for each data stream may be determined byinstructions performed by processor 230. As discussed above, in someaspects, the packet format for one or more streams may be variedaccording to the rank information that is transmitted from the user.

The modulation symbols for all data streams are then provided to a TXMIMO processor 220, which may further process the modulation symbols(e.g., for OFDM). TX MIMO processor 220 then provides N_(T) modulationsymbol streams to N_(T) transceivers (TMTR/RCVR) 222 a through 222 t. Incertain aspects, TX MIMO processor 220 applies precoding weights to thesymbols of the data streams based upon the channel response informationof the user to which the symbols are being transmitted to and theantenna from which the symbol is being transmitted from.

Each transceiver 222 receives and processes a respective symbol streamto provide one or more analog signals, and further conditions (e.g.,amplifies, filters, and upconverts) the analog signals to provide amodulated signal suitable for transmission over the MIMO channel. N_(T)modulated signals from transceivers 222 a through 222 t are thentransmitted from N_(T) antennas 224 a through 224 t, respectively.

At receiver system 250, the transmitted modulated signals are receivedby N_(R) antennas 252 a through 252 r and the received signal from eachantenna 252 is provided to a respective transceiver (RCVR/TMTR) 254.Each receiver 254 conditions (e.g., filters, amplifies, anddownconverts) a respective received signal, digitizes the conditionedsignal to provide samples, and further processes the samples to providea corresponding “received” symbol stream.

An RX data processor 260 then receives and processes the N_(R) receivedsymbol streams from N_(R) receivers 254 based on a particular receiverprocessing technique to provide N_(T) “detected” symbol streams. Theprocessing by RX data processor 260 is described in further detailbelow. Each detected symbol stream includes symbols that are estimatesof the modulation symbols transmitted for the corresponding data stream.RX data processor 260 then demodulates, deinterleaves, and decodes eachdetected symbol stream to recover the data for the data stream. Theprocessing by RX data processor 260 is complementary to that performedby TX MIMO processor 220 and TX data processor 214 at transmitter system210.

The channel response estimate generated by RX processor 260 may be usedto perform space, space/time processing at the receiver, adjust powerlevels, change modulation rates or schemes, or other actions. RXprocessor 260 may further estimate the signal-to-noise-and-interferenceratios (SNRs) of the detected symbol streams, and possibly other channelcharacteristics, and provide these quantities to a processor 270. RXdata processor 260 or processor 270 may further derive an estimate ofthe “operating” SNR for the system. Processor 270 then providesestimated channel state information (CSI), which may comprise varioustypes of information regarding the communication link and/or thereceived data stream. For example, the CSI may comprise only theoperating SNR. The CSI is then processed by a TX data processor 278,which also receives traffic data for a number of data streams from adata source 276, modulated by a modulator 280, conditioned bytransceivers 254 a through 254 r, and transmitted back to transmittersystem 210.

In addition, processor 270 may select the index(ces) or entry(ies) thatcorrespond to the matrix(ces) or vector(s) that provide some desiredchannel conditions, e.g. SNR, for the transceiver 254 based upon thesignals received by the receiver. Processor 270 can quantize the indexor entry according to a codebook that is known at transceiver 222. Insome aspects, as described with respect to FIG. 2, five-bit codes may beutilized allowing a wide range of feedback. The codebook size andentries can vary per device, per sector, per cell, or per system and maybe updated over time based upon communication channel conditions, systemupdates, or the like.

At transmitter system 210, the modulated signals from receiver system250 are received by antennas 224, conditioned by transceivers 222,demodulated by a demodulator 240, and processed by a RX data processor242 to recover the CSI reported by the receiver system. The reported CSIis then provided to processor 230 and used to (1) determine the datarates and coding and modulation schemes to be used for the data streamsand (2) to generate various controls for TX data processor 214 and TXMIMO processor 220.

Further, processor 270 may perform all or some of the functionsdiscussed with respect to FIGS. 1-5 with respect to the access terminal.

The techniques described herein may be implemented by various means. Forexample, these techniques may be implemented in hardware, software, or acombination thereof. For a hardware implementation, the processing units(e.g., processors 230 and 270, TX and RX processors 214, 242, 260 and278, and so on) for these techniques may be implemented within one ormore application specific integrated circuits (ASICs), digital signalprocessors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), field programmable gate arrays(FPGAs), processors, controllers, micro-controllers, microprocessors,other electronic units designed to perform the functions describedherein, or a combination thereof.

For a software implementation, the techniques described herein may beimplemented with modules (e.g., procedures, functions, and so on) thatinclude the instructions that may be implemented by one or moreprocessors to perform the functions described herein. The instructionsmay be stored in memory units, e.g., memory 272 in FIG. 6, on aremovable media, or the like that may be read and executed by one ormore processors (e.g., controllers 270). The memory unit(s) may beimplemented within the processor or external to the processor, in whichcase it can be communicatively coupled to the processor via variousmeans as is known in the art. The memory may also be implemented withinthe processor or external to the processor, stored in an externalmemory, in a computer program product, e.g. a cd-rom or other media, bein a memory at an external server, or the like.

While FIG. 6 discusses a MIMO system, the same system may be applied toa multi-input single-output system where multiple transmit antennas,e.g. those on a base station, transmit one or more symbol streams to asingle antenna device, e.g. a mobile station. Also, a single output tosingle input antenna system may be utilized in the same manner asdescribed with respect to FIG. 6.

It should be noted that the concept of channels herein refers toinformation or transmission types that may be transmitted by the accesspoint or access terminal. It does not require or utilize fixed orpredetermined blocks of subcarriers, time periods, or other resourcesdedicated to such transmissions.

The previous description of the disclosed aspects is provided to enableany person skilled in the art to make or use the present invention.Various modifications to these aspects will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other aspects without departing from the spirit or scope ofthe invention. Thus, the present invention is not intended to be limitedto the aspects shown herein but is to be accorded the widest scopeconsistent with the principles and novel features disclosed herein.

What is claimed is:
 1. A wireless communication apparatus, comprising: aprocessor configured to decode signals that are received over two ormore subcarriers of a segment of subcarriers, which is one of aplurality of segments of subcarriers available for communication, and toprovide precoding information for at least one segment of the pluralityof segments based on the received signal, wherein the precodinginformation is applied to at least one symbol of at least one datastream based upon at least one channel response information of a userand wherein the at least one segment is a subband which comprises apredetermined bandwidth; and a transmitter configured to transmit anindex indicative of the precoding information, wherein each segment ofsubcarriers of the plurality of segments of subcarriers has its ownfeedback channel, and wherein the transmitter is configured to feedbackto a receiver the index indicative of the precoding information for eachof the at least one segment on the segment's own feedback channel. 2.The wireless communication apparatus of claim 1, wherein the processoris configured to provide the index indicative of the precodinginformation as information indicative of precoding weights.
 3. Thewireless communication apparatus of claim 2, wherein the processor isconfigured to determine a signal to noise ratio and select theinformation indicative of the precoding weights as a function of thesignal to noise ratio.
 4. The wireless communication apparatus of claim1, wherein the processor is configured to provide the informationindicative of the precoding weights for at least one other segment ofsubcarriers in addition to the segment including the one or moresubcarriers.
 5. The wireless communication apparatus of claim 1, whereinthe segment comprises a subband.
 6. A method of wireless communications,comprising: receiving signals over two or more subcarriers of a segmentof subcarriers, which is one of one or more segments of subcarriers;generating precoding information for at least one segment, based uponthe received signal wherein the precoding information is applied to atleast one symbol of at least one data stream based upon at least onechannel response information of a user and wherein the at least onesegment is a subband which comprises a predetermined bandwidth; andtransmitting an index indicative of the precoding information, whereineach segment of subcarriers of the one or more segments of subcarriershas its own feedback channel, and wherein the transmitting is configuredto feedback to a receiver the index indicative of the precodinginformation for each of the at least one segment on the segment's ownfeedback channel.
 7. The method of claim 6, wherein the generatingcomprises generating the index indicative of the precoding informationas information indicative of precoding weights.
 8. The method of claim7, wherein the generating comprises determining a signal to noise ratioand selecting the information indicative of the precoding weights as afunction of the signal to noise ratio.
 9. The method of claim 6, whereinthe generating comprises generating the index indicative of theprecoding weights for at least one other segment of subcarriers inaddition to the segment including the one or more subcarriers.
 10. Themethod of claim 6, wherein the segment comprises a subband.
 11. Awireless communication device, comprising: means for receiving signalsover two or more subcarriers of a segment of subcarriers, which is oneof one or more segments of subcarriers; means for generating precodinginformation for at least one segment of the one or more segments, basedupon the received signal, wherein the precoding information is appliedto at least one symbol of at least one data stream based upon at leastone channel response information of a user and wherein the at least onesegment is a subband which comprises a predetermined bandwidth; andmeans for transmitting an index indicative of the precoding information,wherein each segment of subcarriers of the one or more segments ofsubcarriers has its own feedback channel, and wherein the means fortransmitting is configured to feedback to a receiver the indexindicative of the precoding information for each of the at least onesegment on the segment's own feedback channel.
 12. The wirelesscommunication apparatus of claim 11, wherein the generating comprisesgenerating the index indicative of the precoding information asinformation indicative of precoding weights.
 13. The wirelesscommunication apparatus of claim 12, wherein the generating comprisesdetermining a signal to noise ratio and selecting the informationindicative of the precoding weights as a function of the signal to noiseratio.
 14. The wireless communication apparatus of claim 11, wherein thegenerating comprises generating the information indicative of theprecoding weights for at least one other segment of subcarriers inaddition to the segment including the one or more subcarriers.
 15. Acomputer program product comprising: a non-transitory computer-readablemedium having instructions stored thereon that when executed cause atleast one computer to: receive signals over two or more subcarriers of asegment of subcarriers, which is one of one or more segments ofsubcarriers; generate precoding information for at least one segment ofthe one or more segments, based upon the received signal, wherein theprecoding information is applied to at least one symbol of at least onedata stream based upon at least one channel response information of auser and wherein the at least one segment is a subband which comprises apredetermined bandwidth; and transmit an index indicative of theprecoding information, wherein each segment of subcarriers of the one ormore segments of subcarriers has its own feedback channel, and whereinthe transmitting is configured to feedback to a receiver the indexindicative of the precoding information for each of the at least onesegment on the segment's own feedback channel.